Water is a mysterious liquid. This is due to the fact that most of its properties are abnormal, i.e. different from other liquids. The reason lies in its special structure, which is due to hydrogen bonds between the molecules, changing with temperature and pressure. Ice has these unique properties. It is worth saying that the determination of density is possible by the formula ρ = m / V. Accordingly, this criterion can be established through a study of the mass of the medium per unit volume.
Let's look at some
properties of ice and water. For example, an anomaly of density. After melting, the ice density increases, passing through a critical mark of 4 degrees, and only after that begins to decrease with increasing temperature. However, in ordinary liquids, it always decreases during the cooling process. This fact finds a completely scientific explanation. The higher the temperature, the greater the speed of the molecules. This leads to pushing them apart, and, accordingly, the substance becomes more friable. The mystery of water is that, despite the increase in the speed of molecules with increasing temperature,
a decrease in its density occurs only at high temperatures.
The second riddle is the question: “Why can ice float on the surface of the water?”, “Why does it not freeze in the rivers to the bottom?” The fact is that the density of ice is lower than that of water. And in the process of melting of any other liquid, its density is lower than that of a crystal. This is due to the fact that in the latter molecules have a certain periodicity and are located regularly. This is characteristic of crystals of any substances. However, besides this, their molecules are “packed” quite tightly. In the process of crystal melting, regularity disappears, which is possible only with a less dense bond of molecules. Accordingly, the density of the substance decreases during the melting process. But this criterion changes quite a bit, for example, when melting metals, it decreases on average by only 3 percent.
However, the density of ice is less than the
density of water immediately ten percent. Therefore, we can say that this jump is anomalous not only in its sign, but also in size.
These riddles are explained by the features of the ice structure. It is a grid of hydrogen bonds, where in each node there are four of them. Therefore, the grid is called quadruple. All angles in it are equal to qT; therefore, it is called tetrahedral. Moreover, it consists of six-membered rings of curved shape.
A feature of the structure of solid water is that packed molecules are loosened in it. If they were closely interconnected, then the ice density would be equal to 2.0 g / cm3, but in reality it is 0.92 g / cm3. From this, the conclusion was to follow that the presence of large spatial volumes should lead to the appearance of instability. In fact, the grid does not become less strong, but it can be rebuilt. Ice is such a strong material that even the ancestors of modern Eskimos learned to build their huts out of it. And to this day, residents of the Arctic use ice concrete as a building material. Accordingly, with increasing pressure, the ice structure changes. It is in this stability that the main property of the hydrogen bonds of the networks between H 2 O molecules lies. Accordingly, each water molecule in the liquid state retains four hydrogen bonds, but at the same time the angles become different from qT, which leads to the fact that the ice density is less than water.